Therapeutic hypothermia, i.e. lowering a patient's body temperature, has been used as a treatment to help reduce the risk of the ischemic injury to tissue following a period of insufficient blood flow, e.g. following a cardiac arrest or stroke. Different systems and methods for inducing such hypothermia have been proposed, such as submersion or enclosure of the body in a cooling bath or wrap, or by routing blood flow out of the body and through a cooling device. In other systems, external cooling of the head through placement of a cap, helmet or collar with cooling mechanisms or flow is proposed. Other approaches have included spraying a volatile liquid perfluorocarbon coolant into the nasal cavity, with evaporation of the coolant decreasing the temperature in the head, or expanding a balloon against internal airway tissues, e.g. with cold liquid.
However, such systems for cooling are not optimal for the purpose of cooling the brain or other specific tissues. Whole-body cooling by way of a bath or wrap risks damage to skin, muscle or other tissues if not carefully administered. It also requires bulky or relatively large devices to cover the body, and overuses cooling insofar as generally the entire body need not be subjected to hypothermia in order to treat the brain or other localized tissues. Routing blood through an external cooling device requires not only sophisticated equipment but also can only be done for a limited time, e.g. the amount of time a patient can sustain a cardiopulmonary bypass. External cooling of the head requires an external fitting that generally must fit closely with the patient's head and/or neck, requiring a number of sizes or adjustability for different patients. It can have also substantial inefficiencies in cooling because of its exposure to the ambient environment. Use of a volatile coolant within the body can present difficulties in terms of monitoring potential toxicity levels of the coolant and ensuring that the coolant remains in parts of the body that will tolerate it. A balloon that seals the airway may not be usable over significant time periods due to its interference with the patient's breathing.
Accordingly, new devices and methods for applying cooling to specific tissues, for example to treat the brain and protect it from adverse effects arising from lack of blood flow (e.g. stroke or cardiac arrest) or from traumatic injury, are needed.